The present invention is directed toward methods and apparatuses for distributing power in microelectronic workpiece processing tools.
Microelectronic workpieces, such as semiconductor wafers, typically undergo several processing steps within a single enclosed environment. For example, microelectronic workpieces can be plated, annealed, etched, and cleaned in a plurality of processing chambers that are located within a single housing or cabinet. These processes can be performed on each workpiece individually in separate single-wafer processing chambers, which is referred to in the industry as xe2x80x9csingle-wafer processing.xe2x80x9d The workpieces are thus typically transferred from one processing station to another within the housing.
FIG. 1 illustrates an apparatus 10 for single-wafer processing in accordance with one embodiment of an LT-210C available from Semitool, Inc. of Kalispell, Mont. The apparatus 10 includes a housing 11 that encloses a plurality of processing chambers 20 and a workpiece loader 12 that receives containers 13 filled with microelectronic workpieces 14. The apparatus 10 also includes a robot 15 that removes the workpieces 14 from the containers 13, moves the workpieces 14 among the processing chambers 20, and returns the processed workpieces 14 to the containers 13.
As shown in FIG. 1, the apparatus 10 includes a central power supply 30 that receives, for example, AC power and converts the AC power to other waveforms for use throughout the tool. For example, the output of the power supply 30 is provided to each of the electrodes in the plating chambers. Additional power supplies are generally used to operate solenoid valves 50 for directing fluid to and from the processing chambers 20, the workpiece loader 12 (to drive the motors and actuators that move and access the containers 13), and to two head controllers 40 (one of which is visible in FIG. 1). The head controllers 40 are coupled to the processing chambers 20 to drive the motors that open, close, and otherwise operate the chambers 20.
The power provided from the power supply 30 to the electrodes in the processing chambers and the power provided from other power sources to other components of the tool are conducted along a power distribution network that typically comprises a variety of cable types that have different electrical characteristics (i.e., physical construction, impedance, electromagnetic coupling, noise immunity, etc.). Although variation in the electrical characteristics of the cables may be tolerable for the power conducted to the motors used in processing chambers, even subtle variations between the electrical characteristics of the power provided to the electrodes in the electrochemical processing chambers can result in substantial differences and inconsistencies in the wafers.
One characteristic of some existing power distribution networks is that the power distribution lines used to provide power to electrodes in a first processing chamber may have different electrical characteristics than the power distribution lines that provide power to electrodes in a second electrochemical processing chamber. Further, the power distribution lines that provide power to the electrodes in the processing chambers may be electromagnetically coupled to other power distribution lines in the power distribution network in some applications. The signals transmitted to one processing chamber over one power line, for example, can be inductively and/or capacitively coupled with signals transmitted to other components. Many applications compensate for such inductive and/or capacitive coupling by shielding the power lines, but even shielding may not provide adequate protection in some instances. As a result, different processing chambers often effectively receive different chemical processing power signals.
The present invention is directed toward methods and apparatuses for processing microelectronic workpieces. The present inventors have recognized that there is a need to provide each of the electrochemical processing chambers in a processing tool with at least substantially the same electrochemical processing power to ensure consistent processing performance between the various electrochemical processing chambers. Further, they have recognized that this can be accomplished by placing a number of power supplies at various locations in a processing tool to reduce the impact that the cables in the power distribution network have upon the effective signals received by the electrodes in the electrochemical processing stations. The present inventors accordingly developed various solutions to the foregoing problems that include, for example, locating a plurality of power supplies throughout a processing apparatus so that the electrical links or other types of power distribution lines between the power supplies and the processing chambers have at least substantially the same electrical characteristics and are not subject to extensive electromagnetic interference from other cables. Therefore, several embodiments of microelectronic processing tools in accordance with the invention provide at least substantially the same effective power to electrodes in electrochemical processing stations for enhancing the consistency in the plating performance of similar electrochemical processing stations.
In one aspect of the invention, the apparatus can include a housing at least partially enclosing a process environment. The housing can include a first processing chamber having a first anode and a first cathode, and a second processing chamber having a second anode and a second cathode. A first power supply can be electrically coupled to the first processing chamber to provide electrical power to at least one of the first anode and the first cathode, and a second power supply can be electrically coupled to the second processing chamber to provide electrical power to at least one of the second anode and the second cathode.
In several embodiments, the first power supply can be dedicated to provide power to the first anode and the first cathode separate from the second power supply, and the second power supply can be dedicated to provide power to the second anode and the second cathode separate from the first power supply. Unlike conventional systems that have a single power supply that provides power to the electrodes in all of the processing stations in a tool using cables of different lengths (and thus impedances), a further aspect of several of these embodiments is that the first power supply can be electrically coupled to the first processing chamber with a conductive link having a first impedance, and the second power supply can be electrically coupled to the second processing chamber with a conductive link having a second impedance at least approximately the same as the first impedance. For example, the first and second conductive links can have approximately the same lengths and/or approximately the same resistances because the first and second power supplies can be located approximately the same distances from the first and second processing stations, respectively. This accordingly is expected to reduce the need to compensate for differences in the signals caused by the links. In a further aspect of the invention, the first and second power supplies can each include an input portion configured to receive electrical power and an output portion configured to transmit electrical power. The output portion of each of the first and second power supplies can be electrically decoupled from all other processing chambers of the housing.
In yet a further aspect of an embodiment of the invention, the first and second power supplies are separated from each other so that the first and second conductive links to the power supplies extend through separate raceways. This feature reduces the number of cables in close proximity to each other, which is expected to reduce inductive and capacitive coupling.
The invention is also directed toward a method for assembling a tool for processing a microelectronic workpiece. In one aspect of the invention, the method can include positioning a first processing chamber in a housing, with the first processing chamber having a first anode and a first cathode and being configured to process a microelectronic workpiece. The method can further include positioning a second processing chamber in the housing, with the second processing chamber having a second anode and a second cathode and being configured to process a microelectronic workpiece. The method can still further include coupling a first output portion of a first power supply to at least one of the first anode and the first cathode, with the first output portion electrically decoupled from the second anode and the second cathode. The method can further include coupling a second output portion of a second power supply to at least one of the second anode and the second cathode, with the second output portion electrically decoupled from the first anode and the first cathode.
The invention is also directed toward a method for processing microelectronic workpieces. In one aspect of the invention, the method can include positioning a first microelectronic workpiece in a first processing chamber located within a housing defining a processing environment, and positioning a second microelectronic workpiece in a second processing chamber located within the housing. The method can further include providing power to at least one of a first anode and first cathode of the first processing chamber from a first output portion of a first power supply, and providing power to at least one of a second anode and a second cathode of the second processing chamber from a second output portion of a second power supply different than the first power supply. The power provided by the first power supply and the second power supply can be provided with the second output portion electrically decoupled from the first anode and the first cathode, and the first output portion electrically decoupled from the second anode and the second cathode.